K3s noise figure spec
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Does anybody KNOW what the noise figure is for the 50MHz preamp on the
K3s? It isn't listed in the specifications. I need to know in order to make system noise figure calculations. My feedline is going to be long (low loss, but long) and I'm trying to determine if I will need a preamp mounted at the antenna. Thanks, Dave, K4TO ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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Dave,
I don't know the answer to your question, but if you use a preamp at the antenna, you will not need to use the preamp in the K3S. The preamp at the the antenna will set the noise figure for the system. The preamp at the K3S end of the feedline will have to consider the feedline loss. At 50 MHz the difference (mast preamp vs. receiver preamp) may be of little concern, but at higher frequencies it can be significant. Many VHF operators run with mast mounted preamps with a separate receive feedline to the receiver - often with RG-58 feedline because the feedline loss is not important for mast mounted preamps. 50 MHz is in the middle ground for that consideration. 73, Don W3FPR On 6/30/2020 7:31 PM, Dave Sublette wrote: > Does anybody KNOW what the noise figure is for the 50MHz preamp on the > K3s? It isn't listed in the specifications. > > I need to know in order to make system noise figure calculations. My > feedline is going to be long (low loss, but long) and I'm trying to > determine if I will need a preamp mounted at the antenna. > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Dave Sublette-2
Dave,
I don't know the NF, but my K3 with PR6 (which the K3s supposedly has internal) has a MDS of -145 dBm at 500-Hz bandwidth. That is fine for 50-MHz on eme (most demanding mode). I have a ARR P50VDG preamp at the base of my 6m-eme tower which provides 0.5 dBNF with 24 dB gain. I run it with PR6 turned off for very slight improvement. The K3s 50-MHz NF is probably fine with internal preamp ON. For comparison my 2m-eme system MDS is -157 dBm (preamp is 0.1 dBNF). But on 144-MHz low NF has more benefit since sky noise is lower (250K vs 2000K on 6m). In truth with the rise in environmental noise, low NF on 2m is getting less effective. 6m-eme folk say this: "If your coax line loss to the antenna is < 1 dB, locating a preamp at the antenna is unnecessary". K3s should do fine without external preamp (in general). BTW my KX3 with internal preamp at 30-dB gain level has equal sensitivity to my K3+PR6. 73, Ed - KL7UW Date: Tue, 30 Jun 2020 19:31:01 -0400 From: Dave Sublette <[hidden email]> To: Elecraft Discussion List <[hidden email]> Subject: [Elecraft] K3s noise figure spec Does anybody KNOW what the noise figure is for the 50MHz preamp on the K3s? It isn't listed in the specifications. I need to know in order to make system noise figure calculations. My feedline is going to be long (low loss, but long) and I'm trying to determine if I will need a preamp mounted at the antenna. Thanks, Dave, K4TO 73, Ed - KL7UW http://www.kl7uw.com Dubus-NA Business mail: [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Dave Sublette-2
On 6/30/2020 4:31 PM, Dave Sublette wrote:
> Does anybody KNOW what the noise figure is for the 50MHz preamp on the > K3s? It isn't listed in the specifications. I don't know, but I'm using an ARR GasFET preamp at the RXIN/OUT patch point, and the ARR 0.5 NF seems to be slightly better than the K3S-series Transverter Interface. Although I own an ARR mast-mount version, I'm afraid to put it at the tower because the 6M antenna is only about 10 ft below the SteppIR that I drive legal limit. :) The loss in my 325 ft of 7/8-in hard line plus coax for rotator loop and jumper at the shack is is a bit less than 1 dB on 6M. 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Dave Sublette-2
The PR6-10 was the latest released preamp as an accessory for the K3 prior
to the K3s with its built in preamp. They are likely very similar. Here's the manual for the preamp: https://ftp.elecraft.com/PR/Manuals%20Downloads/PR6-10%20Owners%20Manual%20Rev%20A.pdf NF is claimed to be 0.7db typical. 73 and stay safe jim ab3cv On Tue, Jun 30, 2020 at 7:34 PM Dave Sublette <[hidden email]> wrote: > Does anybody KNOW what the noise figure is for the 50MHz preamp on the > K3s? It isn't listed in the specifications. > > I need to know in order to make system noise figure calculations. My > feedline is going to be long (low loss, but long) and I'm trying to > determine if I will need a preamp mounted at the antenna. > > Thanks, > > Dave, K4TO > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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I can't speak for E.M.E operations, but from over 60 years of experience on
6M, I can tell you that super sensitive receiver performance is NOT a pre-requisite to working LOTS of DX of 50 MHz. When the band is open, either via E or F2 propagation, signals are usually very "loud". The only "weak" signals are those at the initial start and end of the opening. I remember working a station in Alaska from here in Virginia on SSB, who was running 10 watts to a balcony mounted Saturn-6 halo, barely 10 feet off the ground ! He was +10 dB over S nine for over an hour. SO, don't fret over whether your noise figure is 0.5 dB or 2.5 dB, any decent modern radio will hear just fine. 73, Charlie k3ICH >160 countries confirmed on 6M on SSB & CW ONLY, no PSK-31, FT-8' etc. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Dave Sublette-2
Hi,
Here is a quote of my response to the exact same question in 2017: "Hi, According to the ARRL review in November, 2dB! Deaf no more. AB2TC - Knut" That was from this thread: https://marc.info/?l=elecraft&m=149365913804929&w=2 There was a fairly long follow up discussion that was quite informative (e.g. the chip used is capable of much better performance in a manufacturer's test circuit, but in a practical amplifier will do slightly worse). AB2TC - Knut stengrevics wrote > Does anyone know what the preamp 2 noise figure is on 6 meters? I have > not been able to find it in the owner's manual or in Fred's book. > > Thanks, > > John > WA1EAZ Dave Sublette-2 wrote > Does anybody KNOW what the noise figure is for the 50MHz preamp on the > K3s? It isn't listed in the specifications. > > I need to know in order to make system noise figure calculations. My > feedline is going to be long (low loss, but long) and I'm trying to > determine if I will need a preamp mounted at the antenna. > > Thanks, > > Dave, K4TO > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto: > Elecraft@.qth > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to > lists+1215531472858-365791@.nabble -- Sent from: http://elecraft.365791.n2.nabble.com/ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Jim AB3CV
My, how things have changed! In the mid 60's in SE Asia, in a mobile
troposcatter system [AN/MRC-98], we had 4 receivers that used Western Electric 416B planar triodes with the amazing NF of 3.7 dB at 460 MHz. 73, Fred ["Skip"] K6DGW Sparks NV DM09dn Washoe County On 7/1/2020 6:39 AM, Jim Miller wrote: > The PR6-10 was the latest released preamp as an accessory for the K3 prior > to the K3s with its built in preamp. They are likely very similar. > > Here's the manual for the preamp: > > https://ftp.elecraft.com/PR/Manuals%20Downloads/PR6-10%20Owners%20Manual%20Rev%20A.pdf > > > NF is claimed to be 0.7db typical. > > 73 and stay safe > > jim ab3cv > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Charlie T, K3ICH
On 7/1/2020 8:26 AM, Charlie T wrote:
> I can tell you that super sensitive receiver performance is NOT a > pre-requisite to working LOTS of DX of 50 MHz. But it CAN be critical to working the weakest stations that you might be chasing for an award or a new state, grid, or country. 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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Yes, lots of DX and *all* of the DX are two different things.
Wes N7WS On 7/1/2020 11:26 AM, Jim Brown wrote: > On 7/1/2020 8:26 AM, Charlie T wrote: >> I can tell you that super sensitive receiver performance is NOT a >> pre-requisite to working LOTS of DX of 50 MHz. > > But it CAN be critical to working the weakest stations that you might be > chasing for an award or a new state, grid, or country. > > 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Charlie T, K3ICH
Hello Charlie.
I think if you live in an area where there is high populations of amateurs such as FN20 or NW Europe it does help enormously if you can hear the DX early in the opening before the pileup really gets going. However for most urban or semi urban operators 6m is a noisy band. You only need enough gain to raise your noise floor by 10-15dB when a resonant antenna is connected. Any more than that and you have too much gain and you will be hit very hard by the HUGE signals that are around during a typical 6m opening. This is especially important now that we are all on 50.313/50.323. I must admit that I use an external preamp with my K3S so that I can use a band pass filter and a 2 way splitter (SDR for 50.323). I have 25dB gain and a 0.5dB NF LNA, the whole chain is- 0.5dB for the coax cable,- 1dB for the band pass filter, - 3dB for the splitter and a 6dB attenuator which I take out when on EME. My system noise figure is 2.9 dB for terrestrial and 1.6dB for EME. This is probably better than needed. The background noise on 6m dominates sensitivity. More gain than you need is counterproductive. 73 Conrad PA5Y ________________________________ From: [hidden email] <[hidden email]> on behalf of Charlie T <[hidden email]> Sent: 01 July 2020 17:26 To: [hidden email] <[hidden email]> Subject: Re: [Elecraft] K3s noise figure spec I can't speak for E.M.E operations, but from over 60 years of experience on 6M, I can tell you that super sensitive receiver performance is NOT a pre-requisite to working LOTS of DX of 50 MHz. When the band is open, either via E or F2 propagation, signals are usually very "loud". The only "weak" signals are those at the initial start and end of the opening. I remember working a station in Alaska from here in Virginia on SSB, who was running 10 watts to a balcony mounted Saturn-6 halo, barely 10 feet off the ground ! He was +10 dB over S nine for over an hour. SO, don't fret over whether your noise figure is 0.5 dB or 2.5 dB, any decent modern radio will hear just fine. 73, Charlie k3ICH >160 countries confirmed on 6M on SSB & CW ONLY, no PSK-31, FT-8' etc. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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